A top Chinese military leader on Thursday urged Japan to faithfully carry out its promise to destroy all chemical weapons it had abandoned in China during the Second World War.

Fan Changlong, vice chairman of China's Central Military Commission, visited the Ha'erba Ridge in Dunhua, Northeast China's Jilin Province to inspect the disposal and destruction of Japanese-abandoned chemical weapons.

Fan urged Japan to faithfully carry out its end of the agreement, increase input and speed up destruction work. 

According to a Ministry of National Defense statement, more than 90 sites in 18 provincial-level regions across China have been found to contain abandoned chemical weapons from the former Imperial Japanese Army.

Ha'erba Ridge is the largest burying site known so far in China for chemical weapons. Some 330,000 chemical shells and bombs were discovered at the site and are expected to be completely destroyed by 2022.

The Xinhua News Agency previously reported that at least 2 million tons of chemical weapons had been abandoned.

"There is no accurate count on Japanese-abandoned chemical weapons. Imperial Japanese troops left China at the end of World War II in a hurry. A large portion of the military records were either destroyed by the Japanese troops on purpose or were lost over time," Teng Jianqun, an expert on arms control and disarmament, told the Global Times.

Some of the weapons remain toxic and lethal, and continue to be a threat.

In a high-profile case, one person died and 43 were injured from a mustard gas leak in Qiqihar, Heilongjiang Province in 2003 after five metal cans were excavated at a construction site. The metal cans were later found to have been buried by Japanese troops.

As a signatory to the Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on their Destruction, Japan is obliged to destroy all of its abandoned chemical weapons.

"Japan has left a huge stockpile of chemical weapons in China and the money required to destroy them will be enormous. On the other hand, Sino-Japanese relations are not at its best for Japan to feel comfortable to spend on the project," Teng said.